740 



W. LYNN BROWN AND ARNOLD A. McDOWELL 



1-4 5-8 9-12 13-16 17-20 21-24 25-28 29-32 



DAYS 



Fig. 9. Per cent errors for each sex on successive 4 day periods of reduced cue 

 discrimination training. 



on spatial delayed responses for the same groups. The females were sig- 

 nificantly superior to the males throughout the testing. 



The same subjects were tested by McDowell and Brown (1961b) on a 

 graded series of dot discrimination problems. Analysis of the error data 

 yielded a significant sex X problems interaction (Fig. 11). As the discrimi- 

 nations became increasingly harder, the females became increasingly superior 

 to the males. Figure 12 shows that a similar phenomenon was manifest 

 with respect to the relative radiation dosage groups. The higher the relative 

 radiation dosage, the more efficient was the performance as the discrimi- 

 nations became increasingly more difficult. 



Another study by McDowell and Brown (1961c) involving the same 

 64 subjects concerned peripheral cue discrimination learning. The essential 

 apparatus is shown diagrammatically in Fig. 13. Each subject, to obtain 

 consistently the food reward, was required to respond to one of two identical 

 pieces of plumber's chain, on the basis of how near it was to a discriminable 

 cue. The same two discriminable stimulus blocks were used throughout 48 



